This invention relates to semiconductor devices, and more particularly, to solar cells for directly converting solar energy to electrical energy. In the prior art, solar cells are generally fabricated from single unitary semiconductor crystal bodies of rectangular or round shape. The current capability of the cell is proportional to its radiation collection surface, and the voltage output of a cell is determined by the semiconductor utilized, being typically about 1/2 volt for silicon. Accordingly, many solar cells are generally connected together, in series and parallel, in order to provide a panel having the desired power output.
The interconnection of these cells presents numerous manufacturing problems which prior art researchers have attempted to obviate. For example, U.S. Pat. Nos. 3,411,952 and 3,418,170 disclose wrap-around cell designs in which a P-type conductivity region is provided around the top, one edge, and part of an N-type body portion. A metal electrode is connected to the P-type region on the top, side edge and bottom and another electrode is connected to the N-type region on the bottom. Then the individual cells are soldered to conductive strips on an insulated substrate to provide the desired panel.
Others have attempted to eliminate the soldering step by providing cells having all electrical contacts on the front or light-gathering surface of the cell. This is done by providing contacts at corners of the rectangular bodies as described in U.S. Pat. Nos. 3,359,137 and 3,616,528. However, the process steps for providing these structures are costly and cumbersome since they generally require masking of the cells prior to diffusion, or etching part of a diffused layer subsequent to diffusion on one surface.